2 o 8 Memoir Sears Foundation for Marine Research 



Spiracles: length 2.3, 2.8; distance between 10. i, 10. i. 



Mouth: breadth 12.5, 12.3. 



Nostrils: distance between inner ends 10.4, ii.o. 



Gill openings: lengths, ist 1.2, 1.2; 3rd 1.4, 1.5; 5th 1.2, 1.3; distance between 



inner ends, ist 19.7, 18.8; 5th 13.8, 13.6. 

 First dorsal fin: vertical height 2.0, 2.1; length of base 3.8, 3.9. 

 Second dorsal fin: vertical height 1.6, 1.8; length of base 3.7, 4.0. 

 Pelvics: anterior margin 12.0, 12.0. 

 Distance: from tip of snout to center of cloaca 57.5, 57.1 ; from center of cloaca 



to 1st dorsal 31.3, 32.5; to tip of tail 42.5, 42.9; from rear end of 2nd 



dorsal base to tip of tail 2.8, 2.2. 

 Interspace between: ist and 2nd dorsals 0.9, 1.4. 



Disc lozenge-shaped, about 1.3-1.4 times as broad as long; maximum anterior 

 angle in front of spiracles about 90-105° in females and in young males but about 

 110° in mature males; tip of snout not projecting noticeably; anterior margins of pec- 

 torals weakly convex close anterior to level of eyes in females, considerably more strongly 

 convex in mature males; outer corners abruptly rounded, posterior corners somewhat 

 more broadly rounded, especially in males; posterior margins nearly straight along for- 

 ward two-thirds and gently convex along rearward third. Axis of greatest breadth 66- 

 7 1 "/o of distance rearward from snout toward level of axils of pectorals. Tail with mod- 

 erately broad lateral folds extending its entire length ; its length from center of cloaca 

 to first dorsal about 77-82 7o (small specimens) and about 54-5? % (large) as great 

 as distance from center of cloaca to tip of snout; on adults, total length of tail from 

 center of cloaca 74-75 % as great as distance from center of cloaca to tip of snout. 



Specimens of all sizes usually with 2-4 large thorns on each shoulder, one close 

 to inner end of spiracle and another close in front of orbit; one on posterior part of 

 orbital ridge and 1-3 smaller ones on some specimens; a varying number of small to 

 medium thorns on anterior part of rostral ridge; a single mid-dorsal row of conspicuous 

 thorns on strongly radiate bases extending from nuchal region nearly to first dorsal 

 fin, the largest on disc and the smallest along posterior part of tail, numbering about 

 30-31 on small specimens (i 1-15 anterior to axils of pelvics) but decreasing to about 

 24-27 on half-grown specimens and larger (10-12 anterior to axils of pelvics); also 

 1-3 irregular rows of thornlets developing along either side of anterior part of tail; 

 median areas and anterior margins of pectorals also becoming more or less thorny; 

 interspace between the two dorsals with 1-2 thorns on small specimens but not on 

 large ones. In small specimens, skin of disc largely prickly, the region between and 

 anterior to eyes continuing so to maturity, but half-grown specimens and larger with 

 extensive naked areas on either side of mid-dorsal ridge, abreast of spiracles and eyes, 

 over inner parts of pectorals, and along outer posterior margins; pelvics smooth in small 

 and half-grown specimens, but central parts of posterior lobes of adults with a few small 

 thorns and prickles, more conspicuous in some males than in females; dorsals either 



